Merge topic branch t/mixer into master

Merge topic branch t/mixer into master

A few patches for the sleep subcommand of para_mixer, in particular
the two new options to set the initial mood.

This code has been cooking in next for exactly one month.

* refs/heads/t/mixer:
  mixer: sleep: Fade out before stopping the stream.
  mixer: sleep: Cycle audiod on stop.
  mixer: sleep: Add --initial-mood and --initial-delay.
  mixer: sleep: Always set initial volume and channel.
  mixer: sleep: Improve description of sleep subcommand.